JP-A-2004-25636 (U.S. Pat. No. 6,955,418) discloses an inkjet head as an example of a fluid ejection device for ejecting fluid from a nozzle. The inkjet head is designed to eject ink droplets from plural nozzles toward a recording sheet. The inkjet head has a fluid path unit and a piezoelectric actuator that is stacked on the fluid path unit. The fluid path unit has a common fluid reservoir connected to an ink supply port, and plural pressure chambers that corresponds to respective nozzles and that are disposed in fluid paths extending from the common fluid reservoir to the. The piezoelectric actuator selectively varies the volume of the pressure chambers to impart ejection pressure to ink in the pressure chambers, to thereby eject ink droplets from the nozzles.
When the actuator varies the volume of a pressure chamber, a pressure wave is caused in the pressure chamber, which includes not only an advancing component traveling toward the nozzle as the ejection pressure but also a receding component traveling toward the common fluid reservoir. If the receding component of the pressure wave propagates to another adjacent pressure chamber through the common fluid reservoir, so-called crosstalk problem arises. Therefore, the a damper wall for absorbing the receding component of the pressure wave is provided to face the common fluid reservoir.
Recent tendency of development in the field of a fluid ejection device is directed toward a higher density at which nozzles are arranged. In particular, in case of an inkjet head, the nozzles are desirably arranged at a higher density to make the head smaller in size and obtain an image at a higher resolution. Since there is a limit on the number of the nozzles arrayed into one row, nozzles for one color are likely to be arrayed into multiple rows. However, because the common fluid reservoir in the fluid path unit disclosed in JP-A-2004-25636 is elongated to overlap with a row of pressure chambers communicating therewith when viewed in a plan view, if the pressure chambers are arranged at a higher density and in multiple rows to accommodate the higher density and multiple row arrangement of the nozzles, the width of the common fluid reservoir is reduced. The reduced width of the common fluid reservoir undesirably deteriorates damping effect for the pressure wave occurring in the fluid stored in the common fluid reservoir.